Loans - Consumer, Excluding Credit Card Loans, Delinquency Statistics Junior Lien Home Equity Loans (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	$ 747,508	$ 724,177	$ 726,835
Consumer, excluding credit card
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	294,979	288,449	292,620
Consumer, excluding credit card | Home Equity Junior Lien, Excluding Lines of Credit [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	3,144	3,922
% of 30 days past due to total retained loans	3.34%	3.26%
Consumer, excluding credit card | Home equity - junior lien
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	36,375	40,750
% of 30 days past due to total retained loans	2.20%	2.17%
Consumer, excluding credit card | 30–89 days past due | Home Equity Junior Lien, Excluding Lines of Credit [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	66	86
Consumer, excluding credit card | 30–89 days past due | Home equity - junior lien
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	407	511
Consumer, excluding credit card | 90–149 days past due | Home Equity Junior Lien, Excluding Lines of Credit [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	20	26
Consumer, excluding credit card | 90–149 days past due | Home equity - junior lien
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	126	151
Consumer, excluding credit card | 150 days past due | Home Equity Junior Lien, Excluding Lines of Credit [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	19	16
Consumer, excluding credit card | 150 days past due | Home equity - junior lien
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	267	224
Consumer, excluding credit card | HELOC, Within the revolving period | Home Equity Line of Credit
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	25,252	31,848
% of 30 days past due to total retained loans	1.75%	1.91%
Home equity line of credit, open-ended revolving period	10 years
Home equity line of credit, amortization period	20 years
Consumer, excluding credit card | HELOC, Within the revolving period | 30–89 days past due | Home Equity Line of Credit
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	233	341
Consumer, excluding credit card | HELOC, Within the revolving period | 90–149 days past due | Home Equity Line of Credit
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	69	104
Consumer, excluding credit card | HELOC, Within the revolving period | 150 days past due | Home Equity Line of Credit
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	141	162
Consumer, excluding credit card | HELOCs, Beyond the revolving period | Home Equity Line of Credit
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	7,979	4,980
% of 30 days past due to total retained loans	3.16%	3.03%
Consumer, excluding credit card | HELOCs, Beyond the revolving period | 30–89 days past due | Home Equity Line of Credit
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	108	84
Consumer, excluding credit card | HELOCs, Beyond the revolving period | 90–149 days past due | Home Equity Line of Credit
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	37	21
Consumer, excluding credit card | HELOCs, Beyond the revolving period | 150 days past due | Home Equity Line of Credit
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	$ 107	$ 46